Reinforcing bar joint

ABSTRACT

To avoid the rotation of a sleeve, providing an enhanced joint force. A reinforcing bar joint  1  according to the present invention includes an elliptic-sectioned sleeve  2 , a load transfer rod  3  to be inserted through the sleeve, and wedging means  4 . The sleeve  2  is configured so that end portions of reinforcing bars  5   a,    5   b  can be inserted into openings  6   a,    6   b  formed in respective ends of the sleeve  2  so that the reinforcing bars are arranged in series along an identical line. The load transfer rod  3  can also be inserted therethrough in parallel with the end portions of the reinforcing bars  5   a,    5   b  which are inserted into the sleeve  2.

TECHNICAL FIELD

The present invention relates to a reinforcing bar joint to be used forjoining reinforcing bars.

BACKGROUND ART

Reinforcing bars are main components of reinforced concrete structures(RC structures) and steel-reinforced concrete structures (SRCstructures), and are cut in predetermined lengths so as to be arrangedeasily during configuration on-site. The operation of joiningreinforcing bars on-site is thus indispensable.

There are various types of methods for joining reinforcing bars,including a lap joint, a mechanical coupler, and a gas-pressure weldingjoint. These joints are selected and used as appropriate depending onthe quality required of a structure, working conditions, the diametersof the reinforcing bars being used, and the like.

In this instance, the joining methods mentioned above have respectivedrawbacks and advantages. For example, a lap joint can join reinforcingbars easily by utilizing the bar's adhesion to concrete. Since tworeinforcing bars must be overlapped, it becomes harder to performvarious bar arrangements or secure overlapping lengths of such as thebar diameter increases. Furthermore, a mechanical coupler requiresmanagement on such details as the insert length of the reinforcing barsbeing inserted into the coupler and the fastening torque being applied.A gas-pressure welding joint requires the welder to hold a particularqualification for executing of the gas-pressure welding.

For this reason, bar joining methods that are capable of joiningreinforcing bars easily, without requiring a lapping length, have alsobeen developed.

Nevertheless, among those methods, one method for joining pairs ofmutually parallel reinforcing bars is applicable only to reinforcingbars having fixed spacings, and thus is not sufficiently versatile interms of bar pitch (see patent document 1). Moreover, joining methodsthat use a U-shaped sleeve cannot provide sufficient joint strength (seepatent documents 2 and 3).

Under the circumstances, a joint has been developed that is composed ofan elliptic-sectioned steel sleeve and a wedge member. According to sucha joint, the end portions of two reinforcing bars are inserted into thesleeve from respective opposite directions, and then the wedge membercan be driven into the space between the two reinforcing bars through awedge insertion hole formed in the sleeve to join the reinforcing barstogether (see patent document 4 and non-patent document 1).

In the case where the joint is composed of an elliptic-sectioned steelsleeve and a wedge member, however, two reinforcing bars with their endportions alternately inserted into the elliptic sleeve create a gaptherebetween in the direction orthogonal to the axes of the reinforcingbars.

This precludes the two reinforcing bars from being joined along anidentical line, and a problem exists in that it is difficult to providesufficient clearances between reinforcing bars when a large number ofreinforcing bars are required due to seismic standards or the like.

There has also been the problem that if a tensile force acts on the tworeinforcing bars, the sleeve can be rotated due to the foregoing gap inthe direction that is orthogonal to the axes, thereby loosening theengagement between the reinforcing bars and the wedge member. Therotation of the sleeve also produces a bending moment on the reinforcingbars so that the joined areas can be broken by a tensile load that issmaller than their tensile fracture load.

Furthermore, when reinforcing bars are inserted into the steel sleeveand the wedge member is pressed in, the reinforcing bars will be bent atthe position where the wedge member is driven in, and extend obliquelyfrom the sleeve even if the reinforcing bars have extended straight outfrom the sleeve before the wedge member was pressed in. There has thusbeen a problem that it is difficult to form the bar arrangement asintended, resulting in interference or insufficient spacing between thereinforcing bars.

[Patent Document 1] Publication of Japanese Patent No. 3197079

[Patent Document 2] Japanese Patent Application Laid-Open No. Hei5-156721

[Patent Document 3] Japanese Utility Model Publication No. Hei 3-047052

[Patent Document 4] Japanese Utility Model Publication No. Sho 58-32498

[Non-Patent Document 1] ERICO International Corporation, [searched onAug. 2, 2006], the Internet <URL:http://www.erico.com/products/QuickWedge.asp>

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The present invention has been developed in view of the foregoingcircumstances, and it is thus an object thereof to provide a reinforcingbar joint which is capable of avoiding the rotation of its sleeve,providing an enhanced joining force between reinforcing bars.

Another object of the present invention is to provide a reinforcing barjoint which is capable of suppressing bending of the reinforcing bars atthe position where a wedge member is driven in.

In a reinforcing bar joint according to the present invention, the endportions of two reinforcing bars are inserted into openings in both endsof a sleeve, respectively, so that the reinforcing bars are arranged inseries along an identical line. A load transfer rod is also insertedthrough the sleeve so as to be in parallel with the end portions of therespective reinforcing bars.

Then, a first wedge member is pressed into the space between either oneof the two reinforcing bars and the load transfer rod. A second wedgemember is pressed into the space between the other reinforcing bar andthe load transfer rod.

As a result, when the two reinforcing bars are placed under a tensileload, the tensile load is transferred from one reinforcing bar to theload transfer rod through the first wedge member, and is furthertransferred from the load transfer rod to the other reinforcing barthrough the second wedge member.

In addition to this, since the two reinforcing bars are arranged inseries along an identical line, tensile loads from the respectivereinforcing bars act on the sleeve along the same line of action. Thiseliminates the possibility of rotating the sleeve as heretoforediscussed.

The sleeve is composed of a pair of semicylindrical wall portions whichare arranged with their curved inner surfaces opposing each other, and apair of flat wall portions which extend to corresponding edges of thepair of semicylindrical wall portions. The internal space of the sleeveforms a bar insert space at the side of one of the semicylindrical wallportions, and the end portions of the two reinforcing bars are insertedthereto from both the openings of the sleeve, respectively. The side ofthe other semicylindrical wall portion forms a rod insert space, and theload transfer rod is inserted therethrough from one of the openings intothe other opening of the sleeve. When the end portions of the tworeinforcing bars are inserted into the sleeve and the load transfer rodis inserted through the sleeve, the end portions of the two reinforcingbars and the load transfer rod are placed in parallel in the sleeve.

Wedge insertion holes are formed in each of the flat wall portions so asto lie between one of the reinforcing bars and the load transfer rod andbetween the other reinforcing bar and the load transfer rod.

When the first wedge member is driven into the space between one of thereinforcing bars and the load transfer rod, it bites into and engagesboth the reinforcing bar and the load transfer rod by taking thereaction force from the semicylindrical wall portions of the sleeve.Similarly, when the second wedge member is driven into the space betweenthe other reinforcing bar and the load transfer rod, it bites into andengages both the other reinforcing bar and the load transfer rod.

The first wedge member and the second wedge member have a taperedportion which bites into both the reinforcing bar and the load transferrod as described above. Which of the two is bitten into to a greaterdegree depends primarily on the difference in hardness between the two.If the reinforcing bars are not sufficiently bitten into, the engagingforces between the reinforcing bars and the first wedge member and thesecond wedge member are then insufficient.

It is therefore desirable that the load transfer rod have a hardnessthat is equivalent to or higher than that of the reinforcing bars sothat the first and second wedge members bite into the reinforcing barssufficiently as much as allowable in design.

The load transfer rod may, for example, be made of a straight steel rodhaving a circular cross section.

In this instance, the load transfer rod has only to be arranged beside(on one side of) the two reinforcing bars, which are placed in series,whereas the load transfer rod may sometimes be arranged on both sides ofthe two reinforcing bars. In this case, a first wedge member and asecond wedge member are additionally required. When pressing a pair ofthe first wedge members in, the first wedge members that are inserted onboth sides of the two reinforcing bars are pressed in simultaneously asfar as possible. In the case of a pair of the second wedge members, thesame can be said.

Even given such a modification, there is still no possibility ofrotating the sleeve or bending the reinforcing bars in any direction.

If the first and second wedge members are driven into the space betweenthe reinforcing bars and the load transfer rod, the reinforcing bars cansometimes be bent at the positions where the first and second wedgemembers are driven in, and extend obliquely from the sleeve even if thereinforcing bars have extended straight out from the sleeve prior to thefirst and second wedge members being pressed in.

In such cases, protruding portions protruding toward the peripheries ofthe reinforcing bars are desirably formed on the load transfer rod. As aresult of this, when the first and second wedge members are driven inand the reinforcing bars start to bend accordingly, the protrudingportions formed on the load transfer rod come into contact with theperipheries of the reinforcing bars and suppress the bending of thereinforcing bars.

It should be appreciated that the protruding portions may have anyconfiguration. For example, the load transfer rod may be made of astraight portion and bent portions formed on both ends of the straightportion so that the bent portions form the protruding portions. The loadtransfer rod may also be composed of a rod body and large diameterportions that are detachably attached to both ends of the rod body, thelarge diameter portions having an outer diameter that is greater thanthe rod body, so that the large diameter portions form the protrudingportions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and 1(b) are diagrams showing a reinforcing bar joint 1according to a first embodiment, FIG. 1( a) being a front view, FIG. 1(b) being a sectional view taken along line A-A.

FIG. 2 is a diagram showing a state where reinforcing bars 5 a, 5 b arejoined by the joint 1 completely.

FIGS. 3( a) and 3(b) are diagrams showing a reinforcing bar joint 41according to a second embodiment, FIG. 3( a) being a front view, FIG. 3(b) being a sectional view taken along line B-B.

FIG. 4 is a diagram showing how large diameter portions 44 a and 44 bare attached to both ends of a rod body 45.

FIG. 5 is a diagram showing a state where the protruding portions areabsent and the reinforcing bars 5 a, 5 b are bent.

FIG. 6 is a front view of a reinforcing bar joint according to amodification.

FIGS. 7( a) and 7(b) are diagrams showing a reinforcing bar jointaccording to another modification, FIG. 7( a) being a front view, FIG.7( b) being a sectional view taken along line C-C.

DESCRIPTION OF REFERENCE NUMERALS

-   1, 41 reinforcing bar joint-   2, 72 sleeve-   3, 43, 53, 73 load transfer rod-   4 wedging means-   4 a first wedge member-   4 b second wedge member-   5 a, 5 b reinforcing bar-   9 a, 9 b wedge insertion hole-   44 a, 44 b large diameter portion (protruding portion)-   45 rod body-   52 bent portion (protruding portion)-   54 straight portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a reinforcing bar joint according to the present inventionwill be described with reference to the accompanying drawings. It shouldbe noted that components and the like substantially identical to thoseof conventional technology will be designated by the same referencenumerals, and a description thereof will be omitted.

First Embodiment

FIG. 1 is a diagram showing a reinforcing bar joint according to thepresent embodiment. As shown in the diagram, the reinforcing bar joint 1according to the present embodiment comprises an elliptic-sectionedsleeve 2, a load transfer rod 3 to be inserted through the sleeve, andwedging means 4.

The sleeve 2 is configured so that end portions of reinforcing bars 5 a,5 b can be inserted into openings 6 a, 6 b formed in both ends of thesleeve 2 so that the reinforcing bars are arranged in series along anidentical line. The load transfer rod 3 can also be insertedtherethrough in parallel with the end portions of the reinforcing bars 5a, 5 b which are inserted into the sleeve 2.

The sleeve 2 is composed of a pair of semicylindrical wall portions 7, 7which are arranged with their curved inner surfaces opposing each other,and a pair of flat wall portions 8, 8 which extend to the correspondingedges of the pair of semicylindrical wall portions. Wedge insertionholes 9 a, 9 a are formed in the pair of flat wall portions 8, 8 so asto be opposed to each other. Similarly, wedge insertion holes 9 b, 9 bare formed in the flat wall portions 8, 8 so as to be opposed to eachother.

The load transfer rod 3 is made of a straight steel rod having acircular cross section.

In this instance, the wedging means 4 include a wedge member 4 a as afirst wedge member to be driven into the space between the reinforcingbar 5 a and the load transfer rod 3, and a wedge member 4 b as a secondwedge member to be driven into the space between the reinforcing bar 5 band the load transfer rod 3. The wedge member 4 a is inserted throughthe wedge insertion holes 9 a, 9 a which are formed between thereinforcing bar 5 a and the load transfer rod 3. The wedge member 4 b isinserted through the wedge insertion holes 9 b, 9 b which are formedbetween the reinforcing bar 5 b and the load transfer rod 3.

When the wedge member 4 a is driven into the space between thereinforcing bar 5 a and the load transfer rod 3, it bites into andengages both the reinforcing bar 5 a and the load transfer rod 3 bytaking the reaction force from the semicylindrical wall portions 7, 7 ofthe sleeve 2 respectively. Similarly, when the wedge member 4 b isdriven into the space between the reinforcing bar 5 b and the loadtransfer rod 3, it bites into and engages both the reinforcing bar 5 band the load transfer rod 3.

The wedge member 4 a has a tapered portion which bites into both thereinforcing bar 5 a and the load transfer rod 3 and wedge member 4 b hasa tapered portion which bites into both the reinforcing bar 5 b and theload transfer rod 3, as described above. Which of the two is bitten intoto a greater extent depends primarily on the difference in hardnessbetween the two. If the reinforcing bar 5 a is not sufficiently bitteninto, the engaging force between the reinforcing bars 5 a and the wedgemember 4 a is then insufficient and similarly if the reinforcing bar 5 bis not sufficiently bitten into, the engaging force between thereinforcing bar 5 b and the wedge member 4 b is then insufficient.

It is therefore desirable that the load transfer rod 3 have a hardnessthat is equivalent to or higher than that of the reinforcing bars 5 a, 5b so that the wedge members 4 a, 4 b sufficiently bite into thereinforcing bars 5 a, 5 b as much as allowable in design, respectively.

Specifically, taking an example where the reinforcing bars 5 a, 5 b aremade of SD345 (steel rod for reinforced concrete, Japanese IndustrialStandards (JIS)), the load transfer rod 3 may be made of S45C (carbonsteel for machine structural use, JIS).

When joining the reinforcing bars 5 a, 5 b using the reinforcing barjoint 1 according to the present embodiment, one end portion of thereinforcing bar 5 a is initially inserted into one opening 6 a of thesleeve 2 and one end portion of the reinforcing bar 5 b is inserted intothe other opening 6 b of the sleeve 2.

Simultaneously with or immediately before or after the operation ofinserting the reinforcing bars, the load transfer rod 3 is insertedthrough the sleeve 2. During this inserting operation, the load transferrod 3 is inserted into the sleeve 2 so as to be in parallel with the endportions of the reinforcing bars 5 a, 5 b.

Next, the wedge member 4 a is inserted and pressed into the wedgeinsertion holes 9 a, 9 a, and the wedge member 4 b is inserted andpressed into the wedge insertion holes 9 b, 9 b. To undertake thepress-in, a conventionally known wedge driver may be selected and usedas appropriate.

FIG. 2 is a diagram showing a state where the wedge driving operation iscompleted, resulting in the joining of the reinforcing bars 5 a, 5 bcompletely.

In the reinforcing bar joint 1 according to the present embodiment, theend portions of the two reinforcing bars 5 a, 5 b are inserted into theopenings 6 a, 6 b in both ends of the sleeve 2, respectively, so thatthe reinforcing bars are arranged in series along an identical line. Theload transfer rod 3 is also inserted through the sleeve 2 so as to be inparallel with the end portions of the reinforcing bars, and the twowedge members 4 a, 4 b are pressed in. The wedge member 4 a is pressedinto the space between the reinforcing bar 5 a and the load transfer rod3, and the wedge member 4 b is pressed into the space between thereinforcing bar 5 b and the load transfer rod 3.

Consequently, when the two reinforcing bars 5 a, 5 b are placed under atensile load, the tensile load is transferred from the reinforcing bar 5a to the load transfer rod 3 through the wedge member 4 a, and isfurther transferred from the load transfer rod 3 to the reinforcing bar5 b through the wedge member 4 b.

In addition to this, since the two reinforcing bars 5 a, 5 b arearranged in series along an identical line, tensile loads from therespective reinforcing bars 5 a, 5 b act on the sleeve 2 along the sameline of action.

As has already been described, according to the reinforcing bar joint 1of the present embodiment, the introduction of the load transfer rod 3makes it possible to transfer tensile loads in the situation where thetwo reinforcing bars 5 a, 5 b are arranged in series along an identicalline.

Consequently, the tensile loads from the respective reinforcing bars 5a, 5 b act on the sleeve 2 along the same line of action, therebypreventing the sleeve 2 from being rotated. Moreover, since thereinforcing bars 5 a, 5 b are free from bending ascribable to therotation of the sleeve 2, the reinforcing bars 5 a, 5 b are precludedfrom being broken by tension or by bending without the reinforcing barsexercising their tensile strengths. This makes it possible to fullyexercise the tensile strengths of the reinforcing bars 5 a, 5 b.

It should be appreciated that when the two reinforcing bars 5 a, 5 b areplaced under a tensile load, the tensile load is transferred from thereinforcing bar 5 a to the load transfer rod 3 through the wedge member4 a, and is further transferred from the load transfer rod 3 to thereinforcing bar 5 b through the wedge member 4 b.

This makes it possible to provide sufficient joining strength betweenthe reinforcing bars 5 a, 5 b.

Embodiment 1

The following tensile tests were undertaken in order to examine whateffects the relative difference in hardness between the reinforcing barsand the load transfer rod has on the tensile characteristics of thereinforcing bar joint according to the present invention.

The tensile tests undertaken used wedge members having a wedge length of48 mm, a wedge diameter of 16 mm, and a tip length of 10 mm. Table 1shows specifications of the sleeves.

TABLE 1 thickness wedge of insertion CASE Steel L W W1 H H1 sleeve holeNo. type (mm) (mm) (mm) (mm) (mm) (mm) (mm) 1~5 STKM 13A 140 34 22 56.544.5 6.0 16.5

6 7   8 9 S45C S45C (annealed) S45C S45C (annealed) 220 220   230 23034.4 34.3 34.3 40.0 39.3 40.7 24.9 24.6 24.6 28.0 28.5 29.8 62.7 63.163.0 69.4 69.9 69.6 53.3 53.2 53.5 58.1 58.6 58.0 4.7 4.9 4.8 5.8 5.55.6 16.5

As can be seen from Table 1, the sleeves tested were of three steeltypes: STKM13A (carbon steel for machine structural use, JIS), S45C(non-heat treated), and S45C (annealed). The wedge members were made ofone steel type S45C (refined and hardened).

Next, Table 2 shows the results of the respective tensile tests.

TABLE 2 reinforcing bar load transfer rod tensile tensile tensile sleevestrength strength tensile strength tensile tensile (exper- (Standardstrength (Standard strength strength iment) case diam- steel value)(material) diam- value) (material) (material) [N/ No. eter type [N/mm²][N/mm²] eter steel type [N/mm²] [N/mm²] steel type [N/mm²] results mm²]1 D19 SD345 490 569 D19 SD345 490 569 STKM13A 500.8 base-materialfracture 572.4 base-material fracture 569.8 2 D19 SD345 490 575 D19SD345 490 575 STKM13A 500.8 shear fracture 568.2 3 D19 SD345 490 566 φ19 SNR490B 490 521 STKM13A 500.8 shear fracture 550.1 4 D19 SD345 490566 φ 20 S45C — 812 STKM13A 500.8 base-material fracture 582.2 (refined)base-material fracture 586.4 base-material fracture 586.4 5 D19 SD345490 566 φ 20 SCM435 — 990 STKM13A 500.8 base-material fracture 582.2base-material fracture 587.1 base-material fracture 568.2 6 D22 SD345490 567 φ 24 S45C — 812 S45C 679.4 shear fracture 525.4 (refined) shearfracture 565.2 7 D22 SD390 560 626 φ 23 S45C — 930 S45C 561.7base-material fracture 641.2 (refined (annealed) base-material fracture640.7 and hardened) 8 D25 SD345 490 548 φ 27 S45C — 812 S45C 679.4fracture in 515.5 (refined) wedge potion 9 D25 SD390 560 611 φ 26 S45C —908 S45C 578.3 base-material fracture 614.2 (refined (annealed)base-material fracture 614.2 and hardened)

Cases 1 and 2 were intended to examine the influence of shapevariations, before examining what effects the relative difference inhardness between the reinforcing bars and the load transfer rod has onthe tensile characteristics. In both cases, the load transfer rod wasmade of a deformed bar of steel type (SD345) having the same hardness asthat of the reinforcing bars (SD345) to be joined, but was sourced fromdifferent steel bar producers.

Case 3 was intended to examine the case of using a load transfer rod ofa steel type having the same specification (lower limit) of tensilestrength as that of the reinforcing bars to be joined. The load transferrod was made of steel type SNR490B (rolled steel bar (round bar) forbuilding construction use, JIS).

Cases 4 and 5 were intended to examine the cases of using load transferrods of steel type harder than the reinforcing bars to be joined.Because a round bar is insusceptible to shape-based variations intensile characteristic, the load transfer rods of round shape were used.The load transfer rods were made of steel type S45C (refined) or SCM435.

Cases 7 and 9 were generally the same as cases 4 and 5, and wereintended to examine the cases of using load transfer rods of steel typeharder than the reinforcing bars to be joined. Because a round bar isinsusceptible to shape-based variations in tensile characteristic, theload transfer rods of round shape were used. The load transfer rods weremade of steel type S45C (refined and hardened).

As a result of the tensile test in case 1, the reinforcing bars to bejoined caused base-material fracture. This result shows that deformedbars can be used as the load transfer rod of the joint according to thepresent invention if the load transfer rod has a hardness that isequivalent to that of the reinforcing bars to be joined.

In case 2, the reinforcing bars to be joined caused a shear fracture.This result shows that deformed bars have different tensilecharacteristics because such configurations as a rib diameter, a nodediameter and mechanical characteristics of the actual materialsthemselves vary from one steel bar producer to another.

In case 3, the reinforcing bars to be joined caused a shear fracturebefore base-material fracture. This result shows that when the loadtransfer rod in use has the same specification (lower limit) of tensilestrength as that of the reinforcing bars to be joined (SD345), the SD345may sometimes become harder since actual SD345 materials have greatervariations in tensile strength than those of SNR490B.

In cases 4, 5, 7, and 9, the reinforcing bars to be joined causedbase-material fracture.

From these results, it has been found that the reinforcing bars to bejoined will cause base-material fracture without exception if the loadtransfer rod is made of steel type (S45C (refined), SCM435, S45C(refined and hardened)) that is harder than the reinforcing bars to bejoined (SD345).

The test results of cases 1 to 3, 4, 5, 7, and 9 show that deformed barsas well as round bars of steel types having the same hardness as that ofthe reinforcing bars to be joined can be employed as the load transferrod, however, the load transfer rod might become softer than thereinforcing bars to be joined due to variations in shape ormanufacturing variations in quality. It can thus be said that the loadtransfer rod is desirably selected from among steel types sufficientlyharder than the reinforcing bars to be joined.

However, if the load transfer rod is too hard, the degree to which thewedge members bite into the reinforcing bars increases to increase thedegree of flex of the reinforcing bars accordingly, and the wedgemembers may even be deformed as well. The load transfer rod musttherefore have a hardness such that the degree of biting into thereinforcing bars does not become excessive and also cause deformation ofthe wedge members.

Moreover, in cases 6 and 8 where the sleeve was made of a hard material,the reinforcing bars to be joined caused a shear fracture beforebase-material fracture. The reason for this seems to be that thepress-in of the wedge members does not press the reinforcing barsagainst the inner wall surfaces of the sleeve sufficiently since thesleeve is harder than the reinforcing bars to be joined. In case 8, afracture occurred at the position where a wedge member bit in. Thisseems to be ascribable to the occurrence of a stress concentration atthe biting position of the reinforcing bar. This also shows that even ifthe load transfer rod is harder than the reinforcing bars to be joined,the degree to which the wedge members bite into the reinforcing bars canpossibly be excessive if the sleeve is harder than the reinforcing bars.

From the foregoing test results, it is desirable for the reinforcing barjoint of the present invention that the wedging means be the hardest,and that the load transfer rod, the reinforcing bars to be joined, andthe sleeve be made progressively softer in this order.

It should be noted that, in the foregoing tests, hardness was expressedin terms of tensile strength in order to avoid difficulties incomparison ascribable to different hardness-indicating specifications.

Second Embodiment

A description will now be given of a second embodiment. It should beappreciated that components and the like substantially identical tothose of the foregoing embodiment will be designated by the samereference numerals, and a description thereof will be omitted here.

FIG. 3 is a diagram showing a reinforcing bar joint according to thesecond embodiment. As shown in the diagram, the reinforcing bar joint 41according to the present embodiment comprises an elliptic-sectionedsleeve 2, a load transfer rod 43 to be inserted through the sleeve, andwedging means 4.

The load transfer rod 43 is composed of a rod body 45 and large diameterportions 44 a, 44 b which are protruding portions to be attached torespective ends of the rod body. The large diameter portions 44 a, 44 bare formed to have an outer diameter that is greater than the rod body45, and internal threads are cut in their internal cavities.

Conversely, the rod body 45 is made of a straight steel rod having acircular cross section with external threads in both ends. Theseexternal threads are engaged with the internal threads of the largediameter portions 44 a, 44 b respectively so that the large diameterportions 44 a, 44 b can be detachably attached to the respective ends ofthe rod body 45.

In this instance, the large diameter portions 44 a, 44 b have an outerdiameter determined so that their peripheries come into contact with thereinforcing bars 5 a, 5 b respectively when they are engaged with therespective ends of the rod body 45 which is inserted through the sleeve2. It should be appreciated that the radius of the large diameterportions 44 a, 44 b is made smaller, if necessary, than the distancefrom the axis of the rod body 45 to the peripheries of the reinforcingbars 5 a, 5 b so as not to hinder the operation of screwing the largediameter portions 44 a, 44 b onto the rod body 45.

The wedge members 4 a, 4 b have a tapered portion which bites into boththe reinforcing bar 5 a or 5 b and the load transfer rod 43. Which ofthe two is bitten into to a greater degree depends primarily on thedifference in hardness between the two. If the reinforcing bars 5 a, 5 bare not sufficiently bitten into, the engaging forces between thereinforcing bars 5 a, 5 b and the wedge members 4 a, 4 b are theninsufficient.

It is therefore desirable that the load transfer rod 43 have a hardnessthat is equivalent to or higher than that of the reinforcing bars 5 a, 5b so that the wedge members 4 a, 4 b bite into the reinforcing bars 5 a,5 b as much as allowable in design.

Specifically, taking an example where the reinforcing bars 5 a, 5 b aremade of SD345 (steel rod for reinforced concrete, JIS), the loadtransfer rod 43 may be made of S45C (carbon steel for machine structuraluse, JIS).

The sleeve 2 and the wedging means 4 are the same as used in the firstembodiment, and a description thereof will thus be omitted here.

When joining the reinforcing bars 5 a, 5 b using the reinforcing barjoint 41 according to the present embodiment, one end portion of thereinforcing bar 5 a is initially inserted into one opening 6 a of thesleeve 2 and one end portion of the reinforcing bar 5 b is inserted intothe other opening 6 b of the sleeve 2.

Simultaneously with or immediately before or after the operation ofinserting the reinforcing bars, the rod body 45 of the load transfer rod43 is inserted through the sleeve 2. During this inserting operation,the rod body 45 is inserted into the sleeve 2 so as to be in parallelwith the end portions of the reinforcing bars 5 a, 5 b.

Next, the internal threads of the large diameter portions 44 a, 44 b areengaged with the external threads that are cut in both ends of the rodbody 45, as shown in FIG. 4, so that the peripheries of the largediameter portions 44 a, 44 b make contact with the reinforcing bars 5 a,5 b. It should be appreciated that if the large diameter portions 44 a,44 b are made smaller in radius than the distance from the axis of therod body 45 to the peripheries of the reinforcing bars 5 a, 5 b for theconvenience of the screwing operation, a clearance occurs accordinglyand both members will not be in contact in the strictest sense.

Next, the wedge member 4 a is inserted and pressed into the wedgeinsertion holes 9 a, 9 a, and the wedge member 4 b is inserted andpressed into the wedge insertion holes 9 b, 9 b. To undertake thepress-in, a conventionally known wedge driver may be selected and usedas appropriate.

In the reinforcing bar joint 41 according to the present embodiment, theend portions of the two reinforcing bars 5 a, 5 b are inserted into theopenings 6 a, 6 b in both ends of the sleeve 2, respectively, so thatthe reinforcing bars are arranged in series along an identical line.Meanwhile, the load transfer rod 43 is inserted through the sleeve 2 soas to be in parallel with the end portions of the reinforcing bars, andthe two wedge members 4 a, 4 b are pressed in. The wedge member 4 a ispressed into the space between the reinforcing bar 5 a and the loadtransfer rod 43, and the wedge member 4 b is pressed into the spacebetween the reinforcing bar 5 b and the load transfer rod 43.

Consequently, when the two reinforcing bars 5 a, 5 b are placed under atensile load, the tensile load is transferred from the reinforcing bar 5a to the load transfer rod 43 through the wedge member 4 a, and isfurther transferred from the load transfer rod 43 to the reinforcing bar5 b through the wedge member 4 b.

In addition to this, since the two reinforcing bars 5 a, 5 b arearranged in series along an identical line, tensile loads from therespective reinforcing bars 5 a, 5 b act on the sleeve 2 along the sameline of action.

In this instance, when the wedge members 4 a, 4 b are driven in and thereinforcing bars 5 a, 5 b start to bend, the large diameter portions 44a, 44 b formed on the load transfer rod 43 come into contact with theperipheries of the reinforcing bars 5 a, 5 b and thus suppress thebending of the reinforcing bars.

As has been described, according to the reinforcing bar joint 41 of thepresent embodiment, the new introduction of the load transfer rod 43makes it possible to transfer tensile loads in the situation where thetwo reinforcing bars 5 a, 5 b are arranged in series along an identicalline.

Consequently, tensile loads from the respective reinforcing bars 5 a, 5b act on the sleeve 2 along the same line of action, thereby preventingthe sleeve 2 from being rotated. Moreover, since the reinforcing bars 5a, 5 b are free from bending ascribable to the rotation of the sleeve 2,the reinforcing bars 5 a, 5 b are precluded from being broken by bendingand tension without the reinforcing bars exercising their tensilestrengths. This makes it possible to fully exercise the tensilestrengths of the reinforcing bars 5 a, 5 b.

It should be appreciated that when the two reinforcing bars 5 a, 5 b areplaced under a tensile load, the tensile load is transferred from thereinforcing bar 5 a to the load transfer rod 43 through the wedge member4 a, and is further transferred from the load transfer rod 43 to thereinforcing bar 5 b through the wedge member 4 b.

This makes it possible to provide sufficient joining strength betweenthe reinforcing bars 5 a, 5 b.

Moreover, according to the reinforcing bar joint 41 of the presentembodiment, the ends of the load transfer rod 43 are provided with thedetachable large diameter portions 44 a, 44 b, respectively, and thelarge diameter portions 44 a, 44 b are formed so that the large diameterportions protrude toward the peripheries of the reinforcing bars 5 a, 5b when attached to the respective ends of the load transfer rod 43.Then, when the wedge members 4 a, 4 b are driven in and the reinforcingbars 5 a, 5 b start to bend, the large diameter portions 44 a, 44 bformed on the load transfer rod 43 make contact with the peripheries ofthe reinforcing bars 5 a, 5 b and can thus suppress the bending of thereinforcing bars 5 a, 5 b.

This eliminates the possibility that it may become difficult to form abar arrangement as intended, which would have resulted in interferenceor insufficient spacing between reinforcing bars, as heretoforedescribed.

FIG. 5 schematically shows how the reinforcing bars 5 a, 5 b might bebent. In the absence of the large diameter portions 44 a, 44 b, thepress-in of the wedge members 4 a, 4 b can sometimes bend thereinforcing bars 5 a, 5 b at the driving positions as shown in thediagram. If the large diameter portions 44 a, 44 b are provided,however, the reinforcing bars 5 a, 5 b being bent come into contact withand are restrained by the large diameter portions 44 a, 44 b. As aresult, the bending of the reinforcing bars 5 a, 5 b is suppressed.

In the present embodiment, the protruding portions of the presentinvention, protruding toward the peripheries of the reinforcing bars,are formed as the large diameter portions 44 a, 44 b. Nevertheless, theprotruding portions according to the present invention are not limitedto such a configuration.

For example, as shown in FIG. 6, a load transfer rod 53 composed of astraight portion 54 and bent portions 52, 52 formed on respective endsof the straight portion may be employed so that the bent portions 52, 52form the protruding portions.

Even in such a configuration, when the reinforcing bars 5 a, 5 b startto bend at the driving positions of the wedge members 4 a, 4 b, theextremities of the bent portions 52, 52 come into contact with theperipheries of the reinforcing bars 5 a, 5 b and thus suppress thebending of the reinforcing bars 5 a, 5 b.

In the foregoing embodiments, only a single load transfer rod 3 isinserted through the sleeve 2 so that it is in parallel with the endportions of the reinforcing bars 5 a, 5 b which are inserted into thesleeve 2. Alternatively, as shown in FIG. 7, two load transfer rods 73,73 may both be inserted through a sleeve 72 so that they lie on bothsides of the reinforcing bars 5 a, 5 b in parallel when the end portionsof the reinforcing bars 5 a, 5 b are inserted into the sleeve 2.

In this configuration, the wedging means 4 includes wedge members 4 a, 4a, or first wedge member respectively to be driven into the spacesbetween the reinforcing bar 5 a and the load transfer rods 73, 73, andwedge members 4 b, 4 b, or second wedge member respectively to be driveninto the space between the reinforcing bar 5 b and the load transferrods 73, 73. The wedge members 4 a, 4 a are inserted through wedgeinsertion holes 9 a, 9 a respectively which are formed in flat wallportions of the sleeve 72 between the reinforcing bar 5 a and the loadtransfer rods 73, 73. The wedge members 4 b, 4 b are inserted throughwedge insertion holes 9 b, 9 b respectively which are formed in the flatwall portions of the sleeve 72 between the reinforcing bar 5 b and theload transfer rods 73, 73.

The wedge members 4 a, 4 a and the wedge member 4 b, 4 b are the same asthose detailed in the first embodiment, and a description thereof willthus be omitted here.

Here, while the load transfer rods 3, 53, and 73 and the rod body 45 inthe foregoing embodiments and various modifications thereof are attachedon-site, they may instead be attached to the sleeve 2 or the sleeve 72at a factory or the like in advance.

In the foregoing embodiments and various modifications thereof, thenumber of wedge member 4 a to be pressed into the space between thereinforcing bar 5 a and the load transfer rod 3, and the number of wedgemember 4 b to be pressed into the space between the reinforcing bar 5 band the load transfer rod 3 is one each. In the case of the loadtransfer rod 53 and the load transfer rod 73, the same thing can be saidalso. However, it should be appreciated that more than one of each mayactually be used, and wedge members 4 a may be pressed in along the axesof the reinforcing bars 5 a. In the case of the wedge member 4 b, thesame thing can be said also.

In this regard, the minimum number of wedge members to be pressed in isone for each of the two reinforcing bars. Remaining wedge insertionholes may be left unused.

In such a configuration, unused wedge insertion holes make concretefilling holes during concrete casting, so that concrete flows into thesleeve.

This enhances the strength of the joining reinforcing bars.

1. A reinforcing bar joint comprising: an elliptic-sectioned sleevehaving openings in both ends, end portions of two reinforcing bars beinginsertable into said openings, respectively, so that the reinforcingbars are arranged in series along an identical line; a load transfer rodto be inserted through said sleeve so as to be in parallel with the endportions of said reinforcing bars which are inserted into said sleeve;and a wedging means inserted through wedge insertion holes formed atopposite positions in a pair of flat wall portions constituting saidsleeve, said wedging means comprising a first wedge member to be driveninto a space between either one of said two reinforcing bars and saidload transfer rod, and a second wedge member to be driven into a spacebetween the other reinforcing bar and said load transfer rod.
 2. Thereinforcing bar joint according to claim 1 wherein said load transferrod are arranged on both sides of said two reinforcing bars.
 3. Thereinforcing bar joint according to claim 1 wherein protruding portionsprotruding toward peripheries of said reinforcing bars are formed onsaid load transfer rod.
 4. The reinforcing bar joint according to claim3 wherein said load transfer rod is composed of a straight portion andbent portions formed on respective ends of said straight portion so thatsaid bent portions form said protruding portions.
 5. The reinforcing barjoint according to claim 3 wherein said load transfer rod is composed ofa rod body and large diameter portions that are detachably attached torespective ends of said rod body, said large diameter portions having anouter diameter that is greater than said rod body, so that said largediameter portions form said protruding portions.
 6. The reinforcing barjoint according to claim 1 wherein said load transfer rod has a hardnessthat is relatively higher than that of said reinforcing bars.
 7. Thereinforcing bar joint according to claim 1 wherein said sleeve has ahardness that is relatively lower than that of said reinforcing bars. 8.The reinforcing bar joint according to claim 2 wherein protrudingportions protruding toward peripheries of said reinforcing bars areformed on said load transfer rod.
 9. The reinforcing bar joint accordingto claim 2 wherein said load transfer rod has a hardness that isrelatively higher than that of said reinforcing bars.
 10. Thereinforcing bar joint according to claim 3 wherein said load transferrod has a hardness that is relatively higher than that of saidreinforcing bars.
 11. The reinforcing bar joint according to claim 4wherein said load transfer rod has a hardness that is relatively higherthan that of said reinforcing bars.
 12. The reinforcing bar jointaccording to claim 5 wherein said load transfer rod has a hardness thatis relatively higher than that of said reinforcing bars.
 13. Thereinforcing bar joint according to claim 2 wherein said sleeve has ahardness that is relatively lower than that of said reinforcing bars.14. The reinforcing bar joint according to claim 3 wherein said sleevehas a hardness that is relatively lower than that of said reinforcingbars.
 15. The reinforcing bar joint according to claim 4 wherein saidsleeve has a hardness that is relatively lower than that of saidreinforcing bars.
 16. The reinforcing bar joint according to claim 5wherein said sleeve has a hardness that is relatively lower than that ofsaid reinforcing bars.